Mobile flushing devices for automobiles are known. For example, U.S. Pat. No. 3,431,145 to Reilly shows a wheeled container having plural compartments and a means for injecting air under pressure for forcing fluid in one of the compartments into an automotive cooling system. While many devices of the prior art employ similar principals, there is a need for a flushing apparatus with a mechanism for protection against mistakes in carrying out the flushing operation. In a garage environment, mechanics are frequently interrupted in the middle of a job. In prior art devices, it is difficult to determine the state of a flushing operation, just by viewing the apparatus. An object of the present invention was to devise a flushing apparatus for automotive air conditioning systems whose condition in carrying out the multiple steps of a flushing operation would be apparent by viewing the device. Another object was to devise a compact construction for an air conditioning flushing apparatus which would fit in narrow spaces in an automotive garage.